circadian rhythm

Metabolic syndrome, through its effects on hyperglycemia and dyslipidemia, is associated with several neurodegenerative diseases. Therefore, the aim of the present study was to compare the biological rhythm of the body after 8 weeks of continuous exercise in relation to the risk factors for neuronal degeneration, with a focus on miR-132 as a determinant factor in neurodegenerative disorders.

In this experimental study, 48 male NMRI laboratory mice with an average weight of 26 ± 3.22 grams were included. Initially, 24 mice were randomly selected and fed a high-fat, high-calorie diet (HFD) for 12 weeks, confirming the parameters of metabolic syndrome. The mice were then randomly divided into 6 groups: healthy morning control, healthy afternoon control, metabolic syndrome morning control, metabolic syndrome afternoon control, continuous exercise morning metabolic syndrome, and continuous exercise afternoon metabolic syndrome. During the intervention, the exercise groups underwent 8 weeks of continuous physical activity (5 days per week at 50-60% Vmax intensity) on a treadmill. The levels of miR-132 were measured using the Real-time PCR method, and the β-42 amyloid protein levels in the hippocampus were assessed across all groups. Data analysis was performed using a two-way analysis of variance.

The results of the 8 weeks of continuous exercise on miR-132 expression in the hippocampus of the metabolic syndrome mice showed that the main effect of the group, the main effect of time, and the interaction effect (group × time) on miR-132 protein expression were statistically significant among the study groups. The miR-132 levels in the metabolic syndrome + exercise group were significantly higher than those in the metabolic syndrome group, both in the afternoon (P = 0.001) and in the morning (P = 0.001). No significant difference was observed between the two time points. The Aβ42 protein levels in the metabolic syndrome - exercise group were significantly lower than those in the metabolic syndrome group, both in the afternoon (P = 0.002) and in the morning (P = 0.001). Furthermore, the Aβ42 protein levels in the metabolic syndrome - exercise group were also significantly lower than in the healthy mice group, but only in the afternoon (P = 0.002).

Appropriate timing of continuous exercise, particularly in the afternoon, appears to modify metabolic factors and may serve as a preventive or controlling factor for neurodegenerative diseases. This suggests that it could be a promising candidate for further clinical studies aimed at improving the quality of life for patients with metabolic syndrome.

The circadian rhythm, a regulator of sleep-wake cycles, can lead to metabolic disorders and decreased blood insulin levels when disrupted, thereby increasing the risk of diabetes. This study evaluated the effects of metformin on insulin and glucose levels in rats with streptozotocin (STZ)-induced diabetes under circadian rhythm disruption.

In this study, 36 adult male Wistar rats were divided into two groups: one group was maintained under normal light conditions (12 hours of light/12 hours of dark), while the other group was exposed to continuous light (resulting in circadian rhythm disruption). Diabetes was induced with a single intraperitoneal injection of STZ, and confirmation of diabetes was performed 3 days later using a glucose test. The treatment group received 500 mg/kg of metformin daily for two weeks. At the end of the study, blood samples were collected, and glucose and insulin levels were measured using the ELISA method.

This study demonstrated that circadian rhythm disruption caused by constant light exposure negatively impacts glucose metabolism, leading to increased blood glucose levels and decreased insulin levels. In streptozotocin-induced diabetic rats, two weeks of metformin treatment significantly reduced blood glucose levels, although no significant increase in insulin levels was observed.

Circadian rhythm disruption, characterized by reduced insulin secretion and sensitivity, as well as impaired glucose homeostasis, increases the risk of progression to type 2 diabetes. These results underscore the importance of considering circadian rhythms when determining the timing of medication administration and developing diabetes treatment plans, which could enhance diabetes management.

Brown adipose tissue (BAT) is a specialized type of adipose tissue that dissipates energy as heat and plays a crucial role in body weight regulation. UCP-1 and PGC-1α are key players in the conversion of white adipose tissue (WAT) to BAT. This study aimed to investigate the effects of aerobic exercise performed at different times of the day on the expression of these genes in the adipose tissue of diabetic mice.

In this experimental study, 30 adult male NMRI mice aged 8-10 weeks with an average weight of 26 ± 2.3 grams were randomly divided into six groups (five mice per group): two healthy control groups (light and dark phases), two diabetic control groups (light and dark phases), and two diabetic groups with exercise intervention (light and dark phases). The diabetic groups were fed a high-fat diet and injected with streptozotocin. Aerobic exercise was performed for eight weeks at a moderate intensity (50-60% of maximum running speed). At the end of the study, the expression of UCP-1 and PGC-1α genes in adipose tissue was measured using real-time PCR. Data were analyzed using GraphPad Prism 10 software and ANOVA with a significance level of 0.05

The findings of this study indicate that aerobic exercise performed in the evening significantly increased the expression of PGC-1α in diabetic mice. This increase in gene expression suggests the potential for improving metabolic status in this animal model.

Background & Aims :

One of the areas that need attention in the nursing profession, which can affect various fields of work, professional, care, etc., are temperament and character. Various factors can affect the temperament and character. One of these factors is the circadian rhythms in which most nurses experience disturbances. Considering the importance of examining and evaluating temperament and character in nurses and the effects of circadian rhythm disturbances on them, and given that less attention has been paid to it, this study aims to determine the relationship between circadian rhythm and temperament/character of nurses working in selected teaching hospitals in Tehran, Iran.

Materials & Methods :

This is a descriptive-correlational study with a cross-sectional design. The study population consists of all nurses working in teaching hospitals affiliated to Iran University of Medical Sciences. The study samples were 200 eligible nurses who were selected randomly (by lottery method) from different departments of four hospitals. A demographic form, the morningness-eveningness questionnaire (MEQ), and Cloninger’s temperament and character inventory (TCI) were used to collect data. Data analysis was conducted in SPSS software, version 16.

Results:

 Most of the participants (64%) were neither-type nurses in terms of circadian rhythm. The circadian rhythm in overall had a negative significant correlation with persistence (P=0.039) and self-transcendence (P=0.047). Also, circadian rhythm had a significant relationship with age (P<0.001), sex (P=0.044), employment status (P=0.003), and work experience P<0.001). The dimensions of TCI, including novelty seeking, reward dependence, persistence, self-directedness, cooperativeness, and self-transcendence, had a statistically significant relationship with the demographic characteristics of nurses.

Conclusion :

The circadian rhythm of nurses has a significant negative correlation with some components of TCI. Considering the impact of circadian rhythm on the quality of nursing care, the officials and hospital managers should gain sufficient knowledge of circadian rhythms, identify evening-type nurses, provide training, facilities, and special privileges to nurses, and determine their work shifts according to their circadian rhythms, so that they can improve the quality of patient care and increase patient satisfaction.

Occupational burnout leads to inappropriate physical and psychological results and eventually leaving the job, especially during public health crises and pandemics of infectious diseases such as coronavirus disease 2019 (COVID-19). On the other hand, rotating shifts are considered as one of the most important stressful factors in jobs with shift work. The sleep-wake cycle is affected in these occupations, and there is a direct relationship between circadian rhythms (morning/evening) that are individual characteristics, with this cycle.

This study is considered as a cross-sectional, correlational-descriptive research in which 130 nurses caring for COVID-19 patients in Khorram Abad Hospital were selected by convenience sampling method and included in the study based on the inclusion criteria. The participants completed the demographic information form, Morningness-Eveningness Questionnaire (MEQ) and The Maslach Burnout Inventory (MBI). The collected data were analyzed by SPSS version 16.0.

Most of the samples were female whose age average and standard deviation was 36.75±8.60 years. According to the results, the average score of the frequency and severity of burnout in the dimension of emotional exhaustion (27.77±12.30 and 32.82±8.59, respectively) and in the dimensions of depersonalization was (15.64±4.88 and 19.05±7.22 respectively) was in the high range and in the dimension of personal success (24.58±5.14 and 32.98±10.61) it was in the medium range. According to the results, no significant relationship was observed between the frequency and severity of burnout among nurses with their circadian type, but the mean score of the frequency and severity of occupational burnout among nurses who did not adapt to shift work and circadian rhythm was significantly higher than that of nurses who had this adaptation. (P<0.05).

In this study, nurses caring for COVID-19 patients had a high level of occupational burnout, and non-compliance of shift work with the circadian rhythm was associated with more occupational burnout in nurses. Therefore, it is suggested to pay attention to the adaptation of the day and night shifts of the nurses, especially in the public health crisis and the epidemic of certain diseases, which is accompanied by an increase in the work pressure of the nurses

Circadian rhythms are natural processes that regulate the sleep-wake cycle and are repeated approximately every 24 hours and controlled by an internal circadian clock. Incorrect functioning of the circadian clock system disrupts the normal sleep pattern. The molecular regulation of this system is done by several clock genes, the most important of which is the CLOCK gene that encodes a transcription factor that plays a central role in regulating the molecular circadian clock. In this study, the rs1801260 polymorphism of the CLOCK gene was investigated in Iranian patients with insomnia.

In this study, 60 blood samples were collected from people with profound problems of insomnia, inability to control sleep and irregular sleep as the patient group and 60 samples from people without any history of insomnia or sleep disorder as the control group. Then DNA was extracted and rs1801260 polymorphism was assessed by ARMS-PCR using specific primers for normal and mutated alleles and the results were analyzed.

According to the results, 50% of patients had GG, 36.7% had AG and 13.3% had AA genotype. In the control group, the frequency of GG, AG and AA genotypes was 30%, 26.7% and 43.3%, respectively. Also, this polymorphism is significantly associated with insomnia in patients (p<0.05) and has no significant relationship with gender, age and lifestyle of patients.

These findings show that the rs1801260 polymorphism and the presence of the G allele in this position have a significant relationship with sleep disorder and it seems to play an important role in occurrence of insomnia in the Iranian population. Therefore, checking the CLOCK gene in patient or susceptible people can be helpful for effective prevention and treatment of the disease.

The type of circadian rhythms is essential in maintaining physical and mental health and recovery from the disease. This study aimed to investigate the role of circadian rhythms on sleep quality and corona anxiety in men and women.

Methods & Materials: 

The present study is a descriptive comparative causal description. The statistical population included all 18-50 who participated in the survey online. People who completed the questionnaire online were selected for sampling. The research instruments included the circadian inventory rhythms Horne and Ostberg (1976), Petersburg Quality of Sleep Questionnaire (1989), and Alipour et al.’s (2020) Corona-related Anxiety Scale in the Iranian sample. Multivariate analysis of variance (MANOVA) and the Scheffe test were used to analyze the data.

Ethical Considerations: 

This study was registered with the Ethics Committee Razi University Technology Units Development Center at Institute for Psychoanalytic Studies (No.: 99133).

The results showed that the mean of mental and corona physical anxiety in women and men with evening type is higher than in other classes. Men and women in the evening type have a lower sleep quality than in the morning and middle types. The results also showed significant differences between the types regarding corona anxiety, sleep quality, and sex. The difference between the mean of the morning type and evening types’ mean was more than other differences between the means.

Individual differences in morning-evening types seem to play an essential role in the quality of sleep and the experience of corona anxiety

Mitochondrial function is regulated by the dark-light cycle under physiological and pathological conditions. Time-dependent exercise interventions may affect metabolic health in diabetic patients by regulating hyperglycemia. However, limited data are available about the correlation between the time of exercise and the regulation of muscle circadian rhythm in diabetes conditions. This study aimed to investigate the effect of time of exercise in the dark-light cycle on SIRT1 protein expression and the NAD+/NADH ratio in the gastrocnemius muscle of diabetic mice.

In this experimental study, thirty healthy male NMRI mice were randomly divided into three groups: control, diabetic, and diabetic+exercise. Type 2 diabetes was induced using a combination of a high-fat diet (five weeks) and streptozotocin injection (20 mg/kg body weight). Eight weeks of aerobic exercise with moderate intensity (5 days, 80-60 minutes) were performed on a treadmill at two times of the day, the early light phase (ZT3) at 9:00 AM and the early dark phase (ZT15) at 9:00 PM. Gastrocnemius muscles were collected at two times of the day, and SIRT1 protein expression was evaluated by Western blot analysis. The cellular NAD+/NADH content and glucose concentrations were measured using the colorimetric method. A two-way analysis of variance was used to analyze the data.

Eight weeks of aerobic exercise significantly increased SIRT1 protein and NADH levels (P<0.001) and improved hyperglycemia (P=0.005) only in the early dark phase. Aerobic exercise increased the NAD+/NADH ratio independently of time (P=0.003).

Proper exercise timing in the early dark, along with SIRT1 protein and NAD+ level circadian changes, may strengthen the effects of exercise and correct hyperglycemia more effectively.

The type of circadian rhythms is essential in maintaining physical and mental health and recovery from the disease. This study aimed to investigate the role of circadian rhythms on sleep quality and corona anxiety in men and women.

The present study is a descriptive comparative causal description. The statistical population included all 18-50 who participated in the survey online. People who completed the questionnaire online were selected for sampling. The research instruments included the circadian inventory rhythms Horne and Ostberg (1976), Petersburg Quality of Sleep Questionnaire (1989), and Alipour et al.’s (2020) Corona-related Anxiety Scale in the Iranian sample. Multivariate analysis of variance (MANOVA) and the Scheffe test were used to analyze the data.

This study was registered with the Ethics Committee Razi University Technology Units Development Center at Institute for Psychoanalytic Studies (No.: 99133).

The results showed that the mean of mental and corona physical anxiety in women and men with evening type is higher than in other classes. Men and women in the evening type have a lower sleep quality than in the morning and middle types. The results also showed significant differences between the types regarding corona anxiety, sleep quality, and sex. The difference between the mean of the morning type and evening types’ mean was more than other differences between the means.

Individual differences in morning-evening types seem to play an essential role in the quality of sleep and the experience of corona anxiety

Type of circadian rhythm and also recovery after illness are important to keep individuals healthy. Mental health is an important factor in educational progression of students, so the purpose of present study was to investigate the relationship between Circadian rhythms with Academic Performance, stress, anxiety and depression of students.

Present research is a cross-sectional study conducted on 322 students of Gonabad University of Medical Sciences in 1396. The instruments used were demographic questionnaire, Morningness Eveningness Questionnaire and DASS-21. Data analysis was performed using descriptive statistics, independent t-test and Pearson correlation using SPSS version 16 software.

Results indicated majority of students (82.6%) had a balanced rhythm in terms of circadian rhythm. Also, most of them had a moderate level of stress, anxiety and depression.The results of pearson correlation test showed that there was a significant relationship between circadian rhythms with stress (P = 0.004) and depression (P=0.007), while between the circadian rhythms with academic performance (P=0.61) and anxiety (P=0.19) were not statistically significant.

According the correlation between circadian rhythm with scores of stress and depression of students, necessity of planning and paying more attention to the educational and extracurricular programs is suggested.

In recent years, the issue of weight regulation, energy balance and energy homeostasis, appetite and food intake has always been a major topic of discussion among exercise physiology researchers. On the other hand, due to the close relationship between obesity and various factors related to the regulation of appetite and role of some peptides, many researchers interested to find better understanding on this field. Energy balance regulation is a complex issue and several mechanisms are involved in weight regulation; including genetic, physiological and behavioral factors. The hypothalamus is an important part of the brain that plays an important role in energy balance by secreting neuropeptides and various chemical transmitters. The hypothalamus exerts this regulatory action through two sets of signals. The activity of a group of signals reduces body fat, including serotonin and leptin, while another group of signals increase body fat and this action is done through an appetizing neuropeptide such as neuropeptide Y. Leptin is a peptide  hormone that is mainly synthesized and released by subcutaneous fat cells in a fixed, pulsating manner with a peak secretion at midnight .Leptin levels are highly correlated with circadian rhythms and sleep status. Leptin levels increase during the biological night and peak during the biological morning. In conclusion, it seems that the issue of regulating energy balance and eating behavior or appetite, affected by various neuro-hormonal factors. Exercise intervention is also considered as one of the effective factors in creating a negative energy balance and starting the process of reducing excess body fat. Numerous studies have been performed on the effect of aerobic exercise on weight loss and improvement of some neuro-hormonal factors affecting the regulation of energy balance, but in many of these studies there are conflicting results. One of the less discussed topics is the circadian rhythm and changes in some neuro-hormonal factors at different times of day. The aim of this research was to study effect of circadian rhythm on response of neuropeptide Y and leptin to eight weeks of aerobic training with moderate intensity in non-athlete obese young men.

In a quasi-experimental study with pretest-posttest design, 36 non-athlete obese young men with means of age 25.4±3.3 years, weight 98.3±7.7 kg and body mass index 31.8±1.1 kg/m2 were selected purposely and available. Prior to participation, all subjects read and signed informed, voluntary consent forms. The subjects divided randomly into three equal groups (n=12) of control, morning training and evening training. Training intervention was performed during eight weeks, three sessions and with an intensity of 60-75 percent of maximum heart rate. The aerobic training program started in the first week with an intensity of 60% of the maximum heart rate and then every two weeks the aerobic training was increased by 5%. Each session consisted of 10 minutes warming-up, 40 minutes interval aerobic training and 10 minutes cooling-down. During exercise, the heart rates of subjects were monitored using a Polar heart rate monitor. The morning training and evening training groups, performed aerobic training program at 10 am and 5 pm respectively. During the exercise intervention, the subjects used a similar diet and were prohibited from taking any medications or supplements. Before and after training intervention, blood sampling was performed at 10 hours fasting state. Plasma levels of neuropeptide Y and leptin were analyzed using validated ELISA kits. Data were analyzed by using one-way analysis of variance and at significant level at p<0.05.

The finding of this study indicated that eight weeks of aerobic training intervention in morning and evening caused to significant decrease in plasma levels of leptin (p=0.03) and significant increase in plasma levels of neuropeptide Y (p=0.0001).In comparison between morning and evening training, the changes of Leptin levels (p=0.02) and neuropeptide Y levels (p=0.0001) was more in evening training.

Circadian rhythms are a set of endogenous autonomous oscillators that act to coordinate the body's internal clock in a 24-h day/night cycles and allow different organisms to have adaptation to fluctuating environment. The circadian rhythms are stimulated by the daily changes of light and are followed by hormonal fluctuations; especially the hormones involved in the discussion of appetite. According to the results of this study, eight weeks of aerobic training with moderate intensity causes to changes in plasma levels of neuropeptide Y and leptin hormones, so that these changes in evening training were more than morning training. The lowest concentration of leptin is at noon and the highest is at midnight. This is due to the effects of insulin on leptin and increased glomerular filtration in the morning. It is not yet clear how these circadian rhythm changes affect the role of leptin in weight control. A further decrease in leptin levels in the evening training group is probably related to lower baseline leptin levels at that time. Several mechanisms increase neuropeptide Y. Neuropeptide Y is sensitive to blood glucose and is activated by decreases in blood glucose levels. Aerobic exercise reduces muscle glycogen stores and increases glucose uptake by active muscles. lowering blood glucose levels is significantly associated with increased appetite. Decreases in blood glucose stimulates the secretion of neuropeptide Y. Another mechanism of increase in neuropeptide Y levels is its negative association with leptin levels. As some studies have shown, under positive energy balance conditions, high leptin levels are associated with suppression of neuropeptide Y expression. The results of the present study showed that a decrease in plasma levels of leptin was associated with an increase in plasma levels of neuropeptide Y. In addition, previous investigations have shown that Cortisol and growth hormone are among the most important hormones affecting the increase of leptin levels that are affected by the circadian rhythm. This is probably an explanation for the significant increase in neuropeptide Y levels in the evening training group. One of the limitations of the present study was the lack of evaluation of hormones such as cortisol, insulin and growth hormone, which fluctuate under the influence of circadian rhythms. In conclusion it seems that eight weeks of aerobic training with moderate intensity may have positive effects on changes in neuropeptide Y and leptin hormones involved in the discussion of appetite. These changes seem to be more in the evening training.